This invention relates in general to a method of treating a quartz crystal resonator blank and in particular to a method of shifting the apparent angle of cut of a quartz resonator blank so as to give the quartz resonator a desired frequency versus temperature characteristic.
The frequency versus temperature characteristic of a quartz resonator depends primarily on the angle of cut of the quartz blank with respect to the natural crystallographic axes. The manner in which the frequency versus temperature characteristic depends on the angle of cut as described at pages 77 to 103 of "The Quartz Resonator Handbook-Manufacturing Guide for AT-Type Units," edited by R. E. Bennett, Union Thermoelectric Report, 1960, AD251289. When the quartz resonator is to be used for a TCXO (temperature compensated crystal oscillator), it is particularly important to precisely control the frequency versus temperature characteristic of the quartz resonator. For example, the angle tolerance on a TCXO crystal typically may be about .+-.30 secons of arc. Even if the cutting saw is set for the optimum angle of cut, the various processing operations shift the angles and the finished crystals have a large spread of angles. The angle of cut of each crystal blank is determined by X-ray diffraction, and only those blanks which have angles within the .+-.30 second range are selected for further processing. At the completion of the various processing steps, the number of crystals falling within the .+-.30 second range are, unfortunately, a small fraction of the crystals initially cut.